Grails：对嵌套域对象进行排序

Question

I've got a one to many relationship in.
I have an Application which has multiple files which can be uploaded into it. The Application view contains the Uploaded file list (the files in the list just contain meta data about the file such as file name, file size etc.). I am having trouble with the ability to sort the nested list.
I am using the sortableColumn to call a sort action in my controller.
How can I retrieve an application and specify that the nested list of uploaded files be sorted by the requested attribute (ex. File Name, File Size etc.)

EDIT:
here are some snippets:

Here is the Application Domain Object

class Application implements Serializable {

    private static final long serialVersionUID = 1

    Firm firm

    static hasMany = [applicationDocumentHolders:ApplicationDocumentHolder]

    static belongsTo = [firm:Firm]
    static mapping = {firm lazy: false}
}

And here is the Application Document Holder (I am storing the actual documents in MongoDB and the meta data in SQLServer in an applicationDocumentHolder object, so for the sake of simplicity I am leaving out the document file as it does not pertain to this question)

import java.sql.Time

class ApplicationDocumentHolder implements Serializable {

    private static final long serialVersionUID = 1

    static belongsTo = [application:Application]

    static mapping = {application lazy: false}

    Application application
    ApplicationDocumentType type
    ApplicationDocumentStatus status
    Date verfiedDate
    Long uploadFileId
    //Following fields will be null until a file is uploaded
    String fileName
    Date uploadDate
    String uploadUserId
    long fileSize

    static constraints = {
        type blank: false
        status blank: false
        verfiedDate nullable: true
        uploadFileId nullable: true
        uploadFile nullable: true
        fileName nullable: true
        uploadDate nullable: true
        uploadUserId nullable: true
        fileSize nullable: true
    }
}

Here is a snippet from the GSP where I am using the sortableColumn tag to call the sort action in my controller

<g:sortableColumn action="sort" property="type" title="${message(code: 'applicationDocumentHolder.type.label', default: 'Type')}" />

<g:sortableColumn action="sort" property="status" title="${message(code: 'applicationDocumentHolder.status.label', default: 'Status')}" />

<g:sortableColumn action="sort" property="verfiedDate" title="${message(code: 'applicationDocumentHolder.verfiedDate.label', default: 'Verfied Date')}" />

<g:sortableColumn action="sort" property="fileName" title="${message(code: 'applicationDocumentHolder.uploadFileName.label', default: 'Upload File Name')}" />

I am wondering what the best way to do this is.
I can sort the collection of ApplicationDocumentHolders in the controller but I keep getting violations because these are attached objects to the DB.
I can also re-retrieve the list sorted but I am not sure how you specify that you want a dynamically sorted nested object when it is retrieved from the DB (I know there must be a simple way to do this but I am pretty new to grails).

I would like to know how to do it both way just for future reference.

Answer 1

You can create a simple Closure takes the attribute you want to sort by and the file. You can then Closure.curry(attributeName) that Closure to get a new Closure which sorts by that attribute. Then, pass the Closure to Collection.toSorted() to sort the list of files.

def files = [
    [name: 'foo.txt', size: 10],
    [name: 'bar.txt', size: 30],
    [name: 'hello.txt', size: 20]
]

def sorter = { attr, file -> file[attr] }

files.toSorted sorter.curry('size') // sort by size
files.toSorted sorter.curry('name') // sort by name